Potentiometer



Nov. 26, 1968 J, G. wooos ET AL 3,413,590

POTENTIOMETER Filed July 13, 1967 2 Sheets-Sheet 1 INVENTORS JOHN G.WOODS GEORGE W. WOOD ave 1% ATTORNEY Nov. 26, 1968 Filed July 13, 1967J, cs. wooos ET AL 3,413,590

POTENTIOMETER 2 Sheets-Sheet 2 INVENTORS.

ATTORNEY United States Patent Filed July 13, 1967, Ser. No. 653,067 6Claims. (Cl. 338-180) ABSTRACT OF THE DISCLOSURE A potentiometercomprising a rectangular housing having an enclosed rectangular cavitytherein. A resistance element extends longitudinally along one side wallof the cavity at the bottom of the cavity. The ends of the resistanceelement are mounted in the clip portions of terminals which extend alongthe side wall of the cavity and are secured between the top and bottomwall of the cavity. The terminals have leads extending through thebottom wall of the cavity and project beyond the housing. A collectormember extends longitudinally along the opposite side wall of the cavityand is secured between the top and bottom walls. The collector memberhas a lead extending through the bottom wall and projecting beyond thehousing. A threaded shaft is rotatably supported in the housing andextends longitudinally through the cavity between the resistance elementand collector member. The shaft extends beyond one end of the housing topermit rotation of the shaft. A contact carrier is mounted on the shaftwithin the cavity for longitudinal movement along the shaft uponrotation of the shaft. A contact member is mounted on the contactcarrier for movement therewith. The contact member has one arm slidablyengaging the resistance element and a second arm slidably engaging thecollector member.

Background With the trend toward miniaturization of electronic devices,there has been developed several types of miniature variable resistorsor potentiometers. One such type of miniature potentiometer is therectilinear potentiometer. This type of potentiometer includes anelongated resistance element and an elongated collector member arrangedin parallel, spaced relation in a rectangular housing. A threaded shaftis rotatably supported on the housing and extends parallel to theresistance element and collector member. A contact is mounted on theshaft so that rotation of the shaft moves the contact longitudinallyalong the shaft. The contact slidably engages the resistance element andthe collector member. In designing this type of potentiometer, it isdesirable that the parts of the potentiometer be of simple design andcapable of being easily assembled together. This is of particularimportance in a miniaturized potentiometer wherein the parts areextremely small in size and therefor difficult to handle. In addition,the design of the parts must provide a rugged construction which willoperate properly both mechanically and electrically.

Summary It is an object of the present invention to provide a novelrectilinear potentiometer.

It is another object of the present invention to provide a rectilinearpotentiometer which can be easily assembled so that it is inexpensive tomanufacture.

It is a further object of the present invention to provide a rectilinearpotentiometer having a novel resistance element and terminal mountingmeans therefor.

It is a still further object of the present invention to provide arectilinear potentiometer having a novel contact and means forassembling the contact on a contact carrier.

Other objects will appear hereinafter.

Brief description of the drawings For the purpose of illustrating theinvention, there is shown in the drawings a form which is presentlypreferred; it being understood, however, that this invention is notlimited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a perspective view of the potentiometer of the presentinvention.

FIGURE 2 is a top plane view of the potentiometer of the presentinvention with the cover removed.

FIGURE 3 is a longitudinal, sectional view taken along line 33 of FIGURE2.

FIGURE 4 is a longitudinal sectional view taken along line 4-4 of FIGURE2.

FIGURE 5 is a transverse, sectional view taken along line 55 of FIGURE3.

FIGURE 6 is a perspective view of the contact carrier of thepotentiometer of the present invention.

Description of the invention Referring to the drawings, thepotentiometer of the present invention is generally designated as 10. Ingeneral, the potentiometer 10 comprises a rectangular housing 12, aresistance element 14 mounted in and extending longitudinally along aside Wall of the housing 12, a collector member 16 mounted in andextending longitudinally along the other side wall of the housing, athreaded shaft 18 is rotatably mounted on the housing and extendslongitudinally therethrough between the resistance element 14 and thecollector member 16, and a contact 20 carried on the shaft and slidablyengaging the resistance element 14 and the collector member 16. Rotationof the shaft 18 moves the contact 20 longitudinally in the housing 12 tovary the resistance value of the potentiometer 10.

The housing 12 comprises a rectangular bottom section 22 and arectangular cover plate 24, both of an electrical insulating material,such as a plastic or ceramic. The bottom section 22 has a rectangularcavity 26 in its top surface to provide the bottom section 22 with apair of parallel side walls 28 and 30, a front end wall 32, a rear endwall 34 and a bottom wall 36. The front end wall 32 and rear end wall 34have aligned, longitudinally extending bearing grooves 38 and 40respectively in their top surfaces. The bearing groove 38 extendscompletely across the front end wall 32 whereas the bearing groove 40extends only partly across the rear end Wall 34 from its inner surface.A retainer groove 42 is provided in the top surface of the front endwall 32 and extends transversely across the bearing groove 38. Alongitudinally extending guide groove 44 is provided in the innersurface of the bottom Wall 36 in alignment with the bearing grooves 38and 40.

The cover plate 24 extends over and is secured to the top surface of thebottom section 22 so as to enclose the cavity 26. The cover 24 may besecured to the bottom section 22 by a suitable cement. The cover 24 hasa shallow, rectangular cavity 46 in its inner surface which mates withthe cavity 26 in the bottom section 22. A longi tudinally extendingguide groove 48 is provided in the top surface of the cavity 46 directlyover the guide groove 44 in the bottom wall 36. A retainer groove 49 isprovided in the bottom surface of the cover plate at the front end ofthe cover plate. The retainer groove 49 mates with the retainer groove42 in the front end wall 36 of the bottom section 22.

Resistance element 14 comprises a rod of an electrically insulatingmaterial, such as a plastic or ceramic, which is shown to besubstantially D-shaped, in transverse cross section, and a resistancematerial on the surface of the rod. The resistance material may be afilm of any well-known resistance material coated on the surface of. therod or a resistance wire helically wound around the rod. No matter whattype of resistance material is used, it should provide a longitudinallyextending path along the curved surface of the rod. The resistanceelement 14 is mounted in a pair of terminals 50. Although the rod isshown as having a flat surface to help properly position the rod, therod can be circular in transverse cross-section.

Each of the terminals 50 comprises a flat strip of electricallyconductive metal having a tapered lead portion 52 at one end, a retainerarm 54 extending upwardly from the top end of the mounting portion, anda curved clip portion 56 at the top end of the lead portion along sideof the bottom end of the retainer arm 54. The terminals 50 extend alongthe inner surface of the side wall 28 of the housing 12 at the end walls32 and 34. The terminals 50 extend through narrow openings 58 in thebottom wall 36 so that the clip portions 56 are seated on the bottomwall and the lead portions 52 project beyond the bottom wall. Theretainer arms 54 are of a length to extend to the inner surface of thecover plate 24 so that the terminals 50 are held in place between thebottom wall 36 and the cover plate 24. The terminals 50 at the oppositeends of the resistance element 14 are identical except that the clipportions 56 are on opposite sides of the retainer arms so that the clipportions are adjacent their respective end Walls of the housing. Theends of the resistance element 14 are seated in the clip portions 56 sothat the resistance element is clamped between the clip portion 56 andthe retainer arm 54 of each of the terminals 50.

The collector member 16 comprises a flat rectangular strip 60 of anelectrically conductive metal seated on the bottom wall 36 of thehousing '12 and extending along the side wall 30 between the end walls32 and 34. As shown in FIGURE 4, the height of the collector strip 60 issubstantially equal to the height of the resistance element 14. At theends of the collector strip 60, retainer arms 62 extend perpendicularlyfrom the collector strip to the cover plate 24. The end edges of theretainer arms 62 fit into grooves 64 and 66 in the inner surfaces of theend walls 32 and 34 respectively (see FIGURE 2). A tapered lead 68extends from the bottom edge of the collector strip 60 through anopening 70 in the bottom wall 36 of the housing 12 and projects beyondthe bottom wall. The collector member 16 is held against the bottom wallof the housing 12 by the cover plate 24 engaging the retainer arms 62and is held against lateral movement by the retainer arms fitting in thegrooves 64 and 66.

Shaft 18 has a bearing portion 72 at one end which is rotatablysupported in the bearing groove 40 in the rear end wall 34 of thehousing 12, and a bearing portion 74 adjacent its other end whichextends through and is rotata'bly supported in the bearing groove 38 inthe front end wall 32 of the housing. Thus, the shaft 18 extendslongitudinally across the cavity 26 in the housing 12 parallel to and inbetween the resistance element 14 and contact member 20. Between thebearing portions 72 and 74, the shaft 18 has a threaded portion 76. Atthe front bearing portion 74, the shaft 18 has an annular flange 78which fits into the mating retainer grooves 42 and 49 in the front endwall 32 and cover plate 24. This prevents longitudinal movement of theshaft 18 with respect to the housing 12 but permits the shaft to rotatewith respect to the housing. The front end of the shaft 18 projectsbeyond the front end wall 32 of the housing 12 and has an enlarged head80 thereon by which the shaft can be rotated.

A substantially Y-shaped contact carrier 82 of an electrical insulatingmaterial, such as a plastic, is mounted within the cavity 26 in thehousing 12 between the resistance element 14 and the collector member16. As shown in FIGURE 6, the contact carrier 82 has a substantiallyrectangular leg 84 and a U-shaped head 86 on the top of the leg 84.Aligned notches 88 are provided in the top edges of the arms of the head86 and a notch 90 is provided in the bottom edge of the leg 84 invertical alignment with the notches 88. The contact carrier 82 is seatedin the cavity 26 of the housing 16 with the bottom edge of the leg 84fitting in the guide groove 44 in the bottom wall 36, the arms of thehead 86 encompassing the threaded portion 76 of the shaft 18, and thetop ends of the arms of the head fitting in the guide groove 48 in thecover plate 24. The inner surface of the head 86 of the contact carrier82 is threaded to mate with the threaded portion 76 of the shaft 18. Thethreads may be preformed in the head 86 or the head may grip the threadsof the shaft sufficiently tight so that the shaft threads form thethreads in the surface of the head. Since the contact carrier 82 isprevented from rotating by the guide grooves 44 and 48, rotation of theshaft 18 causes the contact carrier to move longitudinally along theshaft. Contact 20 comprises a substantially U-shaped strip of anelectrically conductive metal having a rounded base 92 and a pair ofarms 94 and 96 extending from the base 92. The arms 94 and 96 haveoutwardly extending contact projections 98 and 100 respectively adjacenttheir free ends, and inwardly extending fingers 102 and 104 respectivelyat their free ends. As shown in FIGURE 5, the contact 20 is mounted onthe contact carrier 82 with the base 92 extending across the open top ofthe head 86 and fitting in the notches 88, and the arms 94 and 96extending downwardly along the leg 84. The arms 94 and 96 normallydiverge from each other. When mounted on the contact carrier 82, thearms 94 and 96 are pressed together until they are substantiallyparallel so that they will fit between the resistance element 14 and thecollection member 20. The contact projection 98 on the arm 94 slidablyengages the resistance material on the resistance element 14, and thecontact projection 100 slidably engages the collector strip 60 of thecontact member 16. The resiliency of the arms 94 and 96 holds theprojections 98 and 100 against the resistance element and collectorstrip respectively. The fingers 102 and 104 fit into the notch 90 in theleg 84 of the contact carrier '82 so as to prevent tilting of thecontact 20 with respect to the contact carrier. As the contact carrier82 is moved longitudinally along the shaft 18 by rotating the shaft, thecontact 20 is moved along the resistance element 14 and collector member16 so as to electrically connect the resistance element to thecollection member.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof, and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

We claim:

1. A potentiometer comprising:

a rectangular housing of an electrical insulating material, said housinghaving an enclosed rectangular cavity therein formed by a pair ofparallel side walls, a pair of end walls extending between the sidewalls, a bottom wall and a top wall;

a resistance element within said cavity and extending along one of saidside walls;

a pair of metal resistance element terminals extending along said oneside wall at the ends of the resistance element and being clampedbetween the top and bottom walls of the housing each of the resistanceelement terminals comprising a fiat strip of an electrically conductivemetal having a retainer arm extending along the one side Wall of thehousing between the top wall and the bottom wall, a lead portionextending from the bottom end of the retainer arm through and projectingbeyond the bottom wall of the housing and a curved clip portion at thetop end of the lead portion and along side of the bottom end of theretainer arm, said clip portion being seated on the bottom wall of thehousing and extending around and engaging the resistance element;

a collector member within the cavity and extending along the other sidewall of the housing;

a threaded shaft extending longitudinally through the cavitysubstantially parallel to the resistance element and the collectormember and being rotatably supported in the end walls of the housing,said shaft projecting beyond one end of the housing so as to beaccessible for rotation of the shaft;

a contact carrier within said cavity and engaging the shaft so thatrotation of the shaft moves the contact carrier longitudinally along theshaft; and

a metal contact mounted on said contact carrier and slidably engagingthe resistance element and the collector member.

2. A potentiometer in accordance with claim 1 in which the collectormember comprises a flat, rectangular strip of an electrically conductivemetal seated on the bottom wall and extending along said other side wallbetween the end walls, a separate retainer arm extending perpendicularlyfrom each end of the strip to the top wall, and a lead extending fromthe bottom edge of the strip through and projecting beyond the bottomwall.

3. A potentiometer in accordance with claim 2 in which the end walls ofthe housing have narrow grooves therein extending between the top walland bottom wall adjacent the said other side wall and the ends of theretainer arms of the collector member extend into said grooves.

4. A potentiometer in accordance with claim 1 in which the contactcarrier comprises a body of an electrical in-- sulating material mountedin the cavity between the resistance element and collector member andextending around and engaging the threaded shaft, and the contactcomprises a substantially U-shaped strip of an electrically conductivemetal having a rounded base extending across the top of the contactcarrier and over the shaft and a pair of arms extending downwardly alongthe sides of the contact carrier, one of said arms slidably engaging theresistance element and the other of said arms slidably engaging thecollector member.

5. A potentiometer in accordance with claim 4 in which the contactcarrier has a notch in and extending across its bottom surface and eachof the arms of the contact has a finger on its end which extends intothe notch.

6. A potentiometer in accordance with claim 4 in which the arms of thecontact normally diverge from each other but are parallel when mountedon the contact carrier so that the resiliency of the metal holds thearms into en gagement with the resistance element and the collectormember.

References Cited UNITED STATES PATENTS 3,124,779 3/1964 'Caddock et at.338

FOREIGN PATENTS 680,809 2/1964 Canada.

ROBERT K. SCHAEFER, Primary Examiner. H. J. HOHAUSER, AssistantExaminer.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,413,590 November 26, 1968 John G. Woods et a1.

It is certified that error ap patent and that said Letters Paten shmmbelow:

pears in the above identified t are hereby corrected as In the headingto the printed specification, lines 4 and 5,

"IRC, Inc., Philadelphia, Pa." should read TRW Inc., a corporation ofOhio Signed and sealed this 10th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

testing Officer Commissioner of Patents

